De novo DNA methylation controls neuronal maturation during adult hippocampal neurogenesis

Adult neurogenesis enables the life-long addition of functional neurons to the hippocampus and is regulated by both cell-intrinsic molecular programs and behavioral activity. De novo DNA methylation is crucial for embryonic brain development, but its role during adult hippocampal neurogenesis has remained unknown. Here, we show that de novo DNA methylation is critical for maturation and functional integration of adult-born neurons in the mouse hippocampus. Bisulfite sequencing revealed that de novo DNA methyltransferases target neuronal enhancers and gene bodies during adult hippocampal neural stem cell differentiation, to establish neuronal methylomes and facilitate transcriptional up-regulation of neuronal genes. Inducible deletion of both de novo DNA methyltransferases Dnmt3a and Dnmt3b in adult neural stem cells did not affect proliferation or fate specification, but specifically impaired dendritic outgrowth and synaptogenesis of newborn neurons, thereby hampering their functional maturation. Consequently, abolishing de novo DNA methylation modulated activation patterns in the hippocampal circuitry and caused specific deficits in hippocampus-dependent learning and memory. Our results demonstrate that proper establishment of neuronal methylomes during adult neurogenesis is fundamental for hippocampal function

Global ecosystem thresholds driven by aridity

Aridity, which is increasing worldwide because of climate change, affects the structure and functioning of dryland ecosystems. Whether aridification leads to gradual (versus abrupt) and systemic (versus specific) ecosystem changes is largely unknown. We investigated how 20 structural and functional ecosystem attributes respond to aridity in global drylands. Aridification led to systemic and abrupt changes in multiple ecosystem attributes. These changes occurred sequentially in three phases characterized by abrupt decays in plant productivity, soil fertility, and plant cover and richness at aridity values of 0.54, 0.7, and 0.8, respectively. More than 20% of the terrestrial surface will cross one or several of these thresholds by 2100, which calls for immediate actions to minimize the negative impacts of aridification on essential ecosystem services for the more than 2 billion people living in drylands.This research was supported by the European Research Council [ERC grant nos. 242658 (BIOCOM) and 647038 (BIODESERT) awarded to F.T.M.]. M.B. acknowledges support from a Juan de la Cierva Formación grant from the Spanish Ministry of Economy and Competitiveness (FJCI-2018-036520-I). F.T.M. acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041), the Alexander von Humboldt Foundation, and the Synthesis Centre for Biodiversity Sciences (sDiv) of the German Centre for Integrative Biodiversity Research (iDiv). M.D.-B. acknowledges support from the Marie Sklodowska-Curie Actions of the Horizon 2020 Framework Program H2020-MSCA-IF-2016 under REA grant no. 702057. S.S. was supported by the Spanish Government under a Ramón y Cajal contract (RYC-2016- 20604). N.G. was supported by the AgreenSkills+ fellowship program, which has received funding from the EU’s Seventh Framework Programme under grant no. FP7-609398 (AgreenSkills+ contract). V.M. was supported by FRQNT-2017-NC-198009 and NSERC Discovery 2016-05716 grants from the government of Canada. H.S. was supported by a Juan de la Cierva Formación grant from the Spanish Ministry of Economy and Competitiveness (FJCI-2015-26782). A.L. and M.C.R. were supported by an ERC Advanced Grant (Gradual Change grant no. 694368) and by the Deutsche Forschungsgesellschaft (grant no. RI 1815/16-1). Y.Z. was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDA19030500)

Establishing an in vitro production program for buffalo embryos (Bubalus bubalis) in Colombia

Objective. Evaluate the results of the standardization of the in vitro production program of buffalo embryos, using oocytes obtained by ultrasound guided oocyte puncture during the 2012 breeding season in Colombia. Materials and methods. Fifty seven buffalo females were selected for ultrasound guided transvaginal aspiration of follicles, oocytes were identified within follicular fluid, classified and transported to the laboratory and matured in vitro for 18 to 20 hours. Frozen semen of seven Mediterranean bulls were used, motile sperm was obtained using the Percoll technique and oocytes were inseminated with 2 million sperm/ml. Presumptive zygotes were cultured for 6 days, grade 1 embryos obtained were frozen using ethylene glycol. Embryos were transferred to females on day 5 during natural cycle. Results. 97 aspirations were performed on the 57 animals, in 8.2% of the aspirations no oocytes were found. 8 oocytes/aspiration were obtained. Of the 783 oocytes, 92% were classified as viable (721/783) and were fertilized. The cleavage and blastocyst rate were 23% and 19% respectively. 37 embryos were transferred and 11 pregnancies were obtained, confirmed by rectal palpation 60 days after transfer, with a pregnancy rate of 29.7%. Conclusions. The results presented here are comparable with others in literature and shows the feasibility of producing in vitro embryos and pregnancies after the standardization of current protocols, with normal and sexed semen and transfer during natural cycle in buffalo.Key words: Buffaloes, embryo, fertilization in vitro, reproduction (Source: MeSH)

Protons in near earth orbit

The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is parameterized by a power law. Below the geomagnetic cutoff a substantial second spectrum was observed concentrated at equatorial latitudes with a flux ~ 70 m^-2 sec^-1 sr^-1. Most of these second spectrum protons follow a complicated trajectory and originate from a restricted geographic region.Comment: 19 pages, Latex, 7 .eps figure

A Study of Cosmic Ray Secondaries Induced by the Mir Space Station Using AMS-01

The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle physics experiment that will study cosmic rays in the $\sim 100 \mathrm{MeV}$ to $1 \mathrm{TeV}$ range and will be installed on the International Space Station (ISS) for at least 3 years. A first version of AMS-02, AMS-01, flew aboard the space shuttle \emph{Discovery} from June 2 to June 12, 1998, and collected $10^8$ cosmic ray triggers. Part of the \emph{Mir} space station was within the AMS-01 field of view during the four day \emph{Mir} docking phase of this flight. We have reconstructed an image of this part of the \emph{Mir} space station using secondary $\pi^-$ and $\mu^-$ emissions from primary cosmic rays interacting with \emph{Mir}. This is the first time this reconstruction was performed in AMS-01, and it is important for understanding potential backgrounds during the 3 year AMS-02 mission.Comment: To be submitted to NIM B Added material requested by referee. Minor stylistic and grammer change

Search for antihelium in cosmic rays

The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 in a 51.7 degree orbit at altitudes between 320 and 390 km. A total of 2.86 * 10^6 helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of < 1.1 * 10^-6 is obtained.Comment: 18 pages, Latex, 9 .eps figure

Isotopic Composition of Light Nuclei in Cosmic Rays: Results from AMS-01

The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper we present measurements of the isotopic ratios 2H/4He, 3He/4He, 6Li/7Li, 7Be/(9Be+10Be) and 10B/11B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.Comment: To appear in ApJ. 12 pages, 11 figures, 6 table

Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP

Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events. Decay-plane correlations, consistent with zero and with the Standard Model predictions, are measured

Ultrarelativistic sources in nonlinear electrodynamics

The fields of rapidly moving sources are studied within nonlinear electrodynamics by boosting the fields of sources at rest. As a consequence of the ultrarelativistic limit the delta-like electromagnetic shock waves are found. The character of the field within the shock depends on the theory of nonlinear electrodynamics considered. In particular, we obtain the field of an ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure